The Cheshire Cat is a fictional cat popularised by Lewis Carroll in Alice's Adventures in Wonderland and known for its distinctive mischievous grin. While most often celebrated in "Alice"-related contexts, the Cheshire Cat predates the 1865 novel and has transcended the context of literature and become enmeshed in popular culture, appearing in various forms of media, from political cartoons to television. One of its distinguishing features is that from time to time its body disappears, the last thing visible being its iconic grin. There are numerous theories about the origins of the phrase "Grinning like a Cheshire Cat" in English history. A possible origin of the phrase is one favoured by the people of Cheshire, a county in England which boasts numerous dairy farms; hence the cats grin because of the abundance of milk and cream. According to Brewer's Dictionary, "The phrase has never been satisfactorily accounted for, but it has been said that cheese was formerly sold in Cheshire moulded like a cat that looked as though it was grinning". The cheese was cut from the tail end, so that the last part eaten was the head of the smiling cat
Reference: Wikipedia